thread.cpp

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    HANDLE        m_hThread;    // handle of the thread
    wxThreadState m_state;      // state, see wxThreadState enum
    unsigned int  m_priority;   // thread priority in "wx" units
    DWORD         m_tid;        // thread id

    // number of threads which need this thread to remain alive, when the count
    // reaches 0 we kill the owning wxThread -- and die ourselves with it
    LONG m_nRef;

    DECLARE_NO_COPY_CLASS(wxThreadInternal)
};

// small class which keeps a thread alive during its lifetime
class wxThreadKeepAlive
{
public:
    wxThreadKeepAlive(wxThreadInternal& thrImpl) : m_thrImpl(thrImpl)
        { m_thrImpl.KeepAlive(); }
    ~wxThreadKeepAlive()
        { m_thrImpl.LetDie(); }

private:
    wxThreadInternal& m_thrImpl;
};


THREAD_RETVAL THREAD_CALLCONV wxThreadInternal::WinThreadStart(void *param)
{
    THREAD_RETVAL rc;

    wxThread * const thread = (wxThread *)param;

    // first of all, check whether we hadn't been cancelled already and don't
    // start the user code at all then
    const bool hasExited = thread->m_internal->GetState() == STATE_EXITED;

    if ( hasExited )
    {
        rc = (THREAD_RETVAL)-1;
    }
    else // do run thread
    {
        // store the thread object in the TLS
        if ( !::TlsSetValue(gs_tlsThisThread, thread) )
        {
            wxLogSysError(_("Can not start thread: error writing TLS."));

            return (DWORD)-1;
        }

        rc = (THREAD_RETVAL)thread->Entry();
    }

    thread->OnExit();

    // save IsDetached because thread object can be deleted by joinable
    // threads after state is changed to STATE_EXITED.
    bool isDetached = thread->IsDetached();

    if ( !hasExited )
    {
        // enter m_critsect before changing the thread state
        wxCriticalSectionLocker lock(thread->m_critsect);
        thread->m_internal->SetState(STATE_EXITED);
    }

    // the thread may delete itself now if it wants, we don't need it any more
    if ( isDetached )
        thread->m_internal->LetDie();

    return rc;
}

void wxThreadInternal::SetPriority(unsigned int priority)
{
    m_priority = priority;

    // translate wxWidgets priority to the Windows one
    int win_priority;
    if (m_priority <= 20)
        win_priority = THREAD_PRIORITY_LOWEST;
    else if (m_priority <= 40)
        win_priority = THREAD_PRIORITY_BELOW_NORMAL;
    else if (m_priority <= 60)
        win_priority = THREAD_PRIORITY_NORMAL;
    else if (m_priority <= 80)
        win_priority = THREAD_PRIORITY_ABOVE_NORMAL;
    else if (m_priority <= 100)
        win_priority = THREAD_PRIORITY_HIGHEST;
    else
    {
        wxFAIL_MSG(wxT("invalid value of thread priority parameter"));
        win_priority = THREAD_PRIORITY_NORMAL;
    }

    if ( !::SetThreadPriority(m_hThread, win_priority) )
    {
        wxLogSysError(_("Can't set thread priority"));
    }
}

bool wxThreadInternal::Create(wxThread *thread, unsigned int stackSize)
{
    wxASSERT_MSG( m_state == STATE_NEW && !m_hThread,
                    _T("Create()ing thread twice?") );

    // for compilers which have it, we should use C RTL function for thread
    // creation instead of Win32 API one because otherwise we will have memory
    // leaks if the thread uses C RTL (and most threads do)
#ifdef wxUSE_BEGIN_THREAD

    // Watcom is reported to not like 0 stack size (which means "use default"
    // for the other compilers and is also the default value for stackSize)
#ifdef __WATCOMC__
    if ( !stackSize )
        stackSize = 10240;
#endif // __WATCOMC__

    m_hThread = (HANDLE)_beginthreadex
                        (
                          NULL,                             // default security
                          stackSize,
                          wxThreadInternal::WinThreadStart, // entry point
                          thread,
                          CREATE_SUSPENDED,
                          (unsigned int *)&m_tid
                        );
#else // compiler doesn't have _beginthreadex
    m_hThread = ::CreateThread
                  (
                    NULL,                               // default security
                    stackSize,                          // stack size
                    wxThreadInternal::WinThreadStart,   // thread entry point
                    (LPVOID)thread,                     // parameter
                    CREATE_SUSPENDED,                   // flags
                    &m_tid                              // [out] thread id
                  );
#endif // _beginthreadex/CreateThread

    if ( m_hThread == NULL )
    {
        wxLogSysError(_("Can't create thread"));

        return false;
    }

    if ( m_priority != WXTHREAD_DEFAULT_PRIORITY )
    {
        SetPriority(m_priority);
    }

    return true;
}

wxThreadError wxThreadInternal::Kill()
{
    if ( !::TerminateThread(m_hThread, (DWORD)-1) )
    {
        wxLogSysError(_("Couldn't terminate thread"));

        return wxTHREAD_MISC_ERROR;
    }

    Free();

    return wxTHREAD_NO_ERROR;
}

wxThreadError
wxThreadInternal::WaitForTerminate(wxCriticalSection& cs,
                                   wxThread::ExitCode *pRc,
                                   wxThread *threadToDelete)
{
    // prevent the thread C++ object from disappearing as long as we are using
    // it here
    wxThreadKeepAlive keepAlive(*this);


    // we may either wait passively for the thread to terminate (when called
    // from Wait()) or ask it to terminate (when called from Delete())
    bool shouldDelete = threadToDelete != NULL;

    wxThread::ExitCode rc = 0;

    // we might need to resume the thread if it's currently stopped
    bool shouldResume = false;

    // as Delete() (which calls us) is always safe to call we need to consider
    // all possible states
    {
        wxCriticalSectionLocker lock(cs);

        if ( m_state == STATE_NEW )
        {
            if ( shouldDelete )
            {
                // WinThreadStart() will see it and terminate immediately, no
                // need to cancel the thread -- but we still need to resume it
                // to let it run
                m_state = STATE_EXITED;

                // we must call Resume() as the thread hasn't been initially
                // resumed yet (and as Resume() it knows about STATE_EXITED
                // special case, it won't touch it and WinThreadStart() will
                // just exit immediately)
                shouldResume = true;
                shouldDelete = false;
            }
            //else: shouldResume is correctly set to false here, wait until
            //      someone else runs the thread and it finishes
        }
        else // running, paused, cancelled or even exited
        {
            shouldResume = m_state == STATE_PAUSED;
        }
    }

    // resume the thread if it is paused
    if ( shouldResume )
        Resume();

    // ask the thread to terminate
    if ( shouldDelete )
    {
        wxCriticalSectionLocker lock(cs);

        Cancel();
    }


    // now wait for thread to finish
    if ( wxThread::IsMain() )
    {
        // set flag for wxIsWaitingForThread()
        gs_waitingForThread = true;
    }

    // we can't just wait for the thread to terminate because it might be
    // calling some GUI functions and so it will never terminate before we
    // process the Windows messages that result from these functions
    // (note that even in console applications we might have to process
    // messages if we use wxExecute() or timers or ...)
    DWORD result wxDUMMY_INITIALIZE(0);
    do
    {
        if ( wxThread::IsMain() )
        {
            // give the thread we're waiting for chance to do the GUI call
            // it might be in
            if ( (gs_nWaitingForGui > 0) && wxGuiOwnedByMainThread() )
            {
                wxMutexGuiLeave();
            }
        }

#if !defined(QS_ALLPOSTMESSAGE)
#define QS_ALLPOSTMESSAGE 0
#endif

        result = ::MsgWaitForMultipleObjects
                 (
                   1,              // number of objects to wait for
                   &m_hThread,     // the objects
                   false,          // don't wait for all objects
                   INFINITE,       // no timeout
                   QS_ALLINPUT|QS_ALLPOSTMESSAGE   // return as soon as there are any events
                 );

        switch ( result )
        {
            case 0xFFFFFFFF:
                // error
                wxLogSysError(_("Can not wait for thread termination"));
                Kill();
                return wxTHREAD_KILLED;

            case WAIT_OBJECT_0:
                // thread we're waiting for terminated
                break;

            case WAIT_OBJECT_0 + 1:
                // new message arrived, process it -- but only if we're the
                // main thread as we don't support processing messages in
                // the other ones
                //
                // NB: we still must include QS_ALLINPUT even when waiting
                //     in a secondary thread because if it had created some
                //     window somehow (possible not even using wxWidgets)
                //     the system might dead lock then
                if ( wxThread::IsMain() )
                {
                    // it looks that sometimes WAIT_OBJECT_0 + 1 is
                    // returned but there are no messages in the thread
                    // queue -- prevent DoMessageFromThreadWait() from
                    // blocking inside ::GetMessage() forever in this case
                    ::PostMessage(NULL, WM_NULL, 0, 0);

                    wxAppTraits *traits = wxTheApp ? wxTheApp->GetTraits()
                                                   : NULL;

                    if ( traits && !traits->DoMessageFromThreadWait() )
                    {
                        // WM_QUIT received: kill the thread
                        Kill();

                        return wxTHREAD_KILLED;
                    }
                }
                break;

            default:
                wxFAIL_MSG(wxT("unexpected result of MsgWaitForMultipleObject"));
        }
    } while ( result != WAIT_OBJECT_0 );

    if ( wxThread::IsMain() )
    {
        gs_waitingForThread = false;
    }


    // although the thread might be already in the EXITED state it might not
    // have terminated yet and so we are not sure that it has actually
    // terminated if the "if" above hadn't been taken
    for ( ;; )
    {
        if ( !::GetExitCodeThread(m_hThread, (LPDWORD)&rc) )
        {
            wxLogLastError(wxT("GetExitCodeThread"));

            rc = (wxThread::ExitCode)-1;

            break;
        }

        if ( (DWORD)rc != STILL_ACTIVE )
            break;

        // give the other thread some time to terminate, otherwise we may be
        // starving it
        ::Sleep(1);
    }

    if ( pRc )
        *pRc = rc;

    // we don't need the thread handle any more in any case
    Free();


    return rc == (wxThread::ExitCode)-1 ? wxTHREAD_MISC_ERROR
                                        : wxTHREAD_NO_ERROR;
}

bool wxThreadInternal::Suspend()
{
    DWORD nSuspendCount = ::SuspendThread(m_hThread);
    if ( nSuspendCount == (DWORD)-1 )
    {
        wxLogSysError(_("Can not suspend thread %x"), m_hThread);

        return false;
    }

    m_state = STATE_PAUSED;

    return true;
}

bool wxThreadInternal::Resume()
{
    DWORD nSuspendCount = ::ResumeThread(m_hThread);
    if ( nSuspendCount == (DWORD)-1 )
    {
        wxLogSysError(_("Can not resume thread %x"), m_hThread);

        return false;
    }

    // don't change the state from STATE_EXITED because it's special and means
    // we are going to terminate without running any user code - if we did it,
    // the code in WaitForTerminate() wouldn't work
    if ( m_state != STATE_EXITED )
    {
        m_state = STATE_RUNNING;
    }

    return true;
}

// static functions
// ----------------

wxThread *wxThread::This()
{
    wxThread *thread = (wxThread *)::TlsGetValue(gs_tlsThisThread);

    // be careful, 0 may be a valid return value as well
    if ( !thread && (::GetLastError() != NO_ERROR) )
    {
        wxLogSysError(_("Couldn't get the current thread pointer"));

        // return NULL...
    }

    return thread;
}

bool wxThread::IsMain()
{
    return ::GetCurrentThreadId() == gs_idMainThread || gs_idMainThread == 0;
}

void wxThread::Yield()
{
    // 0 argument to Sleep() is special and means to just give away the rest of
    // our timeslice
    ::Sleep(0);
}

void wxThread::Sleep(unsigned long milliseconds)
{
    ::Sleep(milliseconds);
}

int wxThread::GetCPUCount()
{
    SYSTEM_INFO si;
    GetSystemInfo(&si);

    return si.dwNumberOfProcessors;
}

unsigned long wxThread::GetCurrentId()
{
    return (unsigned long)::GetCurrentThreadId();
}

bool wxThread::SetConcurrency(size_t WXUNUSED_IN_WINCE(level))
{
#ifdef __WXWINCE__
    return false;
#else
    wxASSERT_MSG( IsMain(), _T("should only be called from the main thread") );

    // ok only for the default one
    if ( level == 0 )
        return 0;

    // get system affinity mask first